Population-based Monastir cohort links early-stage breast cancer with lower 10-year mortality

A population-based cohort study of women diagnosed with breast cancer in Monastir, Tunisia, found that diagnosis at stages 0–II was associated with a 22% lower relative risk of death over 10 years than diagnosis at stages III–IV. The researchers followed 1,075 incident cases diagnosed from 2002 through 2014, with vital status available for 959 women by January 2022.

The descriptive cohort used records from the Cancer Registry of the Central Region to identify all breast cancer cases among Monastir residents, regardless of where diagnosis or treatment occurred. Eligible cases were diagnosed between January 2002 and December 2014 and were followed through the Monastir all-cause mortality database until January 2022. Benign and in situ tumors, recurrences, relapses and cases of metastatic progression were excluded.

Kaplan–Meier methods were used to estimate median survival and three-, five- and ten-year survival. Multivariable Cox regression examined baseline characteristics associated with mortality, while joinpoint regression assessed temporal trends in survival. Disease burden was expressed in disability-adjusted life years, or DALYs, calculated as years of life lost plus years lived with disability.

Median survival for the women included in the survival analysis was 187 months, with a 95% confidence interval of 163.7 to 210.2 months. Three-year survival was 77.0% (95% CI, 76.0%–78.0%), five-year survival was 70.0% (95% CI, 69.0%–71.0%), and ten-year survival was 45.2% (95% CI, 43.2%–47.2%). Median survival reached 226 months among women diagnosed at stages 0–I, compared with lower survival as stage increased.

Stage distribution differed by age. Overall, 21.4% of the 1,075 cases were diagnosed at stage IV, including 18.8% of women aged 30–64 and 33.3% of those older than 64. Stage was missing for 74 patients, or 6.9%, and the investigators reported no significant differences between women with complete and missing stage data across the baseline characteristics examined. Ten-year survival was 53.6% for stage 0–I disease and 25.9% for stage IV disease.

Ten-year relative survival increased significantly among women aged 30–64, the age group targeted by Tunisia’s national breast cancer early-detection program. The estimated annual percentage change was 5.37% (95% CI, 2.03%–8.82%; p=0.005), while three- and five-year relative survival remained stable over time. Because the cohort was observational and did not measure program exposure, treatment or other potential confounders, the trend is an association and cannot establish that the program caused the improvement.

The study estimated that diagnosis at stages 0–II rather than stages III–IV was associated with a relative risk of 0.78 for death over 10 years (95% CI, 0.67–0.91; p=0.001), corresponding to a 22% relative risk reduction. The reported number needed to diagnose was nine for preventing one additional death over the 10-year follow-up. For disease burden, the analysis estimated that diagnosing 61 women at stages 0–II rather than stages III–IV would avoid one DALY.

In the main results, the female cohort accounted for 11,800.5 DALYs, comprising 10,362 years of life lost and 1,438.5 years lived with disability; the reported median was 2.7 years (IQR, 1.8–23.0). The abstract listed a different total of 10,665.4 DALYs and a median of 28.0 years, creating an internal numerical discrepancy that is not explained in the supplied article text. A separate male analysis covered 43 patients, of whom 18 died during follow-up, and estimated 241.2 DALYs, including 230 years of life lost and 74.6 years lived with disability.

Several limitations constrain interpretation. Vital status was unavailable for 116 of the 1,075 women, with missingness more common among cases diagnosed in 2002–2004 than in 2011–2014, although baseline comparisons did not identify significant differences between women with complete and missing follow-up data. Registry sources lacked treatment, molecular subtype, comorbidity, recurrence and progression information, preventing evaluation of whether differences in care contributed to the observed survival patterns. Disability weights were taken from a Chinese population and assumed to remain constant despite changes in disease status, so DALY estimates, particularly years lived with disability, require caution. Results from the Monastir governorate also may not generalize to other parts of Tunisia.

Subject of Research: Long-term breast cancer survival and disease burden in Monastir, Tunisia

Article Title: Survival and disease burden of breast cancer (Monastir, Tunisia): A population-based cohort study (2002–2022)

Article References: Zemni, I., Maatouk, A., Boufrikha, W., Bennasrallah, C., Dhouib, W., Kacem, M., Abroug, H., Ben Fredj, M., Bouanene, I., Jridi, I., Arfa, H., Ben Salem, A., Njim, L., Zaied, S., Faleh, R., Sakka, K., Sriha, B., Jaîdane, L., Mehdi, M., & Belguith Sriha, A. (2026). Survival and disease burden of breast cancer (Monastir, Tunisia): A population-based cohort study (2002–2022). PLOS One, 21(10), e0360398. https://doi.org/10.1371/journal.pone.0360398

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360398

Keywords: breast cancer, population-based cohort, cancer survival, stage at diagnosis, Tunisia, Monastir, ten-year mortality, disability-adjusted life years, early detection, cancer registry, Survival, disease